Low-cost Growth Medium Research Articles

Filter cake extract from the beet sugar industry as an economic growth medium for the production of Spirulina platensis as a microbial cell factory for protein

BackgroundBeet filter cake (BFC) is a by-product of sugar beet processing, which is difficult to dispose of and involves severe environmental concerns. Spirulina platensis is a microalga with a high protein content essential for human and animal nutrition. The present study aimed to utilize the beet filter cake extract (BFCE) to produce Spirulina platensis commercially. However, the cultivation of S. platensis on BFCE to produce economically single-cell protein has not been reported previously.ResultsThe batch experiment revealed the maximum dry weight at Zarrouk’s medium (0.4 g/L) followed by 0.34 g/L in the treatment of 75% BFCE. The highest protein content was 50% in Zarrouk’s medium, followed by 46.5% in 25% BFCE. However, adding a higher concentration of 100% BFCE led to a protein content of 31.1%. In the adaption experiment, S platensis showed an increase in dry cell weight and protein content from 25 to 75% BFCE (0.69 g/L to 1.12 g/L and 47.0% to 52.54%, respectively) with an insignificant variation compared to Zarrouk’s medium (p ≤ 0.05), indicating that S. platensis can be economically produced when cultivated on 75% BFCE The predicated parameters from response surface methodology were NaNO3 (2.5 g/L), NaHCO3 (0.67 g/L), BFCE (33%) and pH = 8, which resulted in biomass yield and protein content (0.56 g/L and 52.5%, respectively) closer to that achieved using the standard Zarrouk’s medium (0.6 g/L and 55.11%). Moreover, the total essential amino acid content was slightly higher in the optimized medium (38.73%) than SZM (36.98%).ConclusionsTherefore, BFCE supplemented medium could be used as a novel low-cost alternative growth medium for producing a single-cell protein with acceptable quantity and quality compared to the standard Zarrouk’s medium.Graphical

Laboratory- and Pilot-Scale Cultivation of Tetraselmis striata to Produce Valuable Metabolic Compounds

Marine microalgae are considered an important feedstock of multiple valuable metabolic compounds of high biotechnological potential. In this work, the marine microalga Tetraselmis striata was cultivated in different scaled photobioreactors (PBRs). Initially, experiments were performed using two different growth substrates (a modified F/2 and the commercial fertilizer Nutri-Leaf (30% TN-10% P-10% K)) to identify the most efficient and low-cost growth medium. These experiments took place in 4 L glass aquariums at the laboratory scale and in a 9 L vertical tubular pilot column. Enhanced biomass productivities (up to 83.2 mg L-1 d-1) and improved biomass composition (up to 41.8% d.w. proteins, 18.7% d.w. carbohydrates, 25.7% d.w. lipids and 4.2% d.w. total chlorophylls) were found when the fertilizer was used. Pilot-scale experiments were then performed using Nutri-Leaf as a growth medium in different PBRs: (a) a paddle wheel, open, raceway pond of 40 L, and (b) a disposable polyethylene (plastic) bag of 280 L working volume. Biomass growth and composition were also monitored at the pilot scale, showing that high-quality biomass can be produced, with important lipids (up to 27.6% d.w.), protein (up to 45.3% d.w.), carbohydrate (up to 15.5% d.w.) and pigment contents (up to 4.2% d.w. total chlorophylls), and high percentages of eicosapentaenoic acid (EPA). The research revealed that the strain successfully escalated in larger volumes and the biochemical composition of its biomass presents high commercial interest and could potentially be used as a feed ingredient.

A novel wastewater-derived cascading algal biorefinery route for complete valorization of the biomass to biodiesel and value-added bioproducts

Integration of multiproduct algal biorefineries with wastewater treatment systems could offer a sustainable approach to produce green products in a circular bioeconomy paradigm while keeping the water-energy-environment nexus sustainable. The present study demonstrated a novel biorefinery route employing a newly isolated self-flocculating microalga Chlamydomonas sp. BERC07. Here, the urban wastewater served as a low-cost growth media and improved biomass production (1.24 g/L) by 2-fold with concomitant removal of 100% total nitrogen, 94% total phosphorus, 56% COD, and 41% BOD. To lower the harvesting cost, an inducible sedimentation-based harvesting system was developed by employing the lowest dose of a commercial-grade flocculant, potash alum (0.27 kg/1000L culture) which improved the sedimentation rate of algal flocs by 240-fold with a biomass recovery efficiency of 96–98%. Later, the wastewater-derived biomass was subjected to downstream processing in a cascading fashion for its complete valorization. The biomass yielded 1.83 mg/g of carotenoids and 480 mg/g of lipids. The lipids were transesterified to produce biodiesel which completely met the preset European and American biodiesel quality standards. After carotenoids and lipids extraction, the residual biomass was fermented using Aspergillus niger and Aspergillus oryzae for the very first time. Interestingly, the A. oryzae outcompeted the A. niger and produced 131.6 U/mL of α-amylase along with 375–384 mg/g of mycoproteins utilizing 75–100 g/L of the residual algal biomass as a sole feedstock. All solvents involved in the product recovery were recycled to the primary wastewater, leaving no waste at the end of the processing pipeline. Overall, the data demonstrated a novel and sustainable biorefinery route with the most efficient harvesting and the complete valorization of the biomass, in a zero-waste approach. However, further upscaling, life cycle assessment, and technoeconomic analyses will be required to assess the economic and environmental sustainability of the proposed biorefinery route.

English

The prospects for using Moringa oleifera leaves extract (MLE) supplemented with different concentrations of kanwa or sodium bicarbonate (NaHCO3) as a low-cost alternative growth medium of Spirulina platensis were evaluated in a small-scale outdoor cultivation system. The present study was aimed to evaluate the potential of MLE growth medium enriched with different concentrations (4 or 8 g L-1) of kanwa and NaHCO3 on growth, chlorophyll content, biochemical characteristics, antioxidant compounds and some physico-chemical factors. Jourdan’s standard medium was taken as control. The results showed that the growth parameters such as cell population, biomass dry weight, cell productivity and specific growth rate were positively affected in MLE cultivation medium enriched with kanwa or NaHCO3 at different concentration levels. The addition of urea, kanwa or NaHCO3 in MLE cultivation medium at different concentration levels increased significantly (p< 0.05) the protein content, the peroxidase and polyphenol oxidase activity, the conductivity, pH, total dissolved solids and salinity from 20 to 25 days of cultivation whereas a decrease in carbohydrate and phenol content was recorded during all the period of the experimentation. The highest values of growth parameters were notably in MLE medium supplemented with urea and kanwa at 8 g L-1. The MLE medium enriched with urea and kanwa at 8 g L-1 was shown to be an appropriate growth medium that can be used as a low-cost alternative growth medium for commercial cultivation of S. platensis.   Key words: Antioxidant compounds, biochemical traits, growth, Moringa oleifera leaves extract, physico-chemical factors, Spirulina platensis.

Characterization of a newly isolated cyanobacterium Trichocoleus desertorum BERC08 as a potential feedstock for the algal biorefinery

Cyanobacteria have numerous biotechnological applications in the environment, industry, pharmaceutics, food, feed, and energy which is why future cascading biorefineries are believed to employ cyanobacteria as their feedstock. The present study evaluated the potential of a newly isolated cyanobacterium for its applications in the multiproduct biorefinery. Based on morphology and the gene sequence of 23S rRNA, the strain was identified as Trichocoleus desertorum. Various abiotic growth factors including light, pH, and nutrients were optimized to achieve enhanced biomass production using various wastewaters as low-cost growth media. Accordingly, a 2.24-fold to 6.97-fold higher biomass production (gL-1) and biomass productivity of 0.86 gL-1d-1 with a CO2 fixation rate of 1.576 gL-1d-1 was achieved when cultured in synthetic wastewater. Besides, the impact of wastewater cultivation was studied on the biosynthesis of valuable metabolites including proteins, carbohydrates, lipids, and pigments. Accordingly, the lipid content of the wastewater-cultivated strain was increased from 24 to 30%, and protein content was increased from 27 to 46%. The lipids were trans-esterified to biodiesel which was turned out to be good quality biodiesel, as revealed through GC-MS analysis. Additionally, the wastewater-cultivated strain produced 117.35 mgg-1 (11.73 % of the total dried biomass) of phycobilin in response to nutrient manipulation, where phycocyanin was shown to be the most prominent pigment with a yield of 94.7 mgg-1, which covered 80% of the total pigments. These remarkable features reflected the promising potential of this strain to be employed as a feedstock in the multiproduct biorefinery.

Impact of wastewater cultivation on pollutant removal, biomass production, metabolite biosynthesis, and carbon dioxide fixation of newly isolated cyanobacteria in a multiproduct biorefinery paradigm

The impact of wastewater cultivation was studied on pollutant removal, biomass production, and biosynthesis of high-value metabolites by newly isolated cyanobacteria namely Acaryochloris marina BERC03, Oscillatoria sp. BERC04, and Pleurocapsa sp. BERC06. During cultivation in urabn wastewater, its pH used to adjust from pH 8.0 to 11, offering contamination-free cultivation, and flotation-based easy harvesting. Besides, wastewater cultivation improved biomass production by 1.3-fold when compared to control along with 3.54–4.2 gL-1 of CO2 fixation, concomitantly removing suspended organic matter, total nitrogen, and phosphorus by 100%, 53%, and 88%, respectively. Biomass accumulated 26–36% carbohydrates, 15–28% proteins, 38–43% lipids, and 6.3–9.5% phycobilins, where phycobilin yield was improved by 1.6-fold when compared to control. Lipids extracted from the pigment-free biomass were trans-esterified to biodiesel where pigment extraction showed no negative impact on quality of the biodiesel. These strains demonstrated the potential to become feedstock of an integrated biorefinery using urban wastewater as low-cost growth media.

Low-cost culture medium for biomass production of lactic acid bacteria with probiotic potential destined to broilers

The aim of this study was to evaluate different low-cost culture media for biomass production of 3 potential probiotic L. salivarius strains, which could be destined to broilers at farms. Different formulated media based on whey permeate (WP) supplemented with nitrogenous sources were evaluated: yeast extract (YE), whey hydrolysate (WH) and MnSO4.H2O (Mn), MgSO4.7H2O (Mg). The growth of each strain in the formulated media and the cost was compared with their growth and cost in commercial medium (MRS). L. salivarius DSPV008P did not grow adequately in any of the formulated media. On the other hand, addition of YE and Mn in the formulated media increased L. salivarius DSPV002P and L. salivarius DPSV011P growth. In contrast, WH and Mg addition increased the L. salivarius DSPV002P biomass only. L. salivarius DSPV011P was the only strain that had similar growth performance in MRS as in the selected medium: WP + YE 8g/l + Mn. In this sense, L. salivarius DSPV011P reached a biomass of 9.22 Log (CFU/ml) in the selected formulated medium, with a low-cost growth medium 12 times less than in MRS. Although the effect of supplements added to the culture medium on kinetic parameters are strain dependent, L. salivarius DSPV011P is the strain with the best technological characteristics, capable of growing in a medium based on a by-product of the dairy industry supplemented with YE and Mn and at a much less cost than in MRS medium.

Microwave-assisted pretreatment of harmful algal blooms for microbial oil-centered biorefinery approach

Utilization of harmful algal blooms (HABs) for the cultivation of oleaginous microorganisms can provide dual benefits of mitigating the toxicity from the aquatic reservoirs and generation of copious media for biodiesel production. In the present investigation, microwave-assisted dilute alkali-freeze pretreatment was optimized to develop a low-cost growth medium from HAB dried biomass. The electron micrographs along with the elemental analysis confirmed the efficient breakage of HABs after the microwave-assisted hydrolysis treatment as compared with the acid hydrolysis. Moreover, the sugar analysis revealed ~ 46% higher carbohydrate content in microwave-assisted hydrolysate as compared with acid hydrolysate. The microwave-assisted hydrolysate and conventional dilute acid hydrolysate were then used to cultivate microalga (Chlorella minutissima) and yeast (Trichosporon cutaneum) for biomass and lipid accumulation and compared to artificial media. Microalga showed ~ 1.3- and 2-fold higher dry cell weight (DCW) and lipid content, respectively, while the yeast growth increased by ~ 27% with lipid content of 30%. The fatty acid profiles and biodiesel properties were also amenable to the international biodiesel standards. Hence, the present study provides a proof-of-concept of utilizing HAB hydrolysate for culturing oleaginous microorganisms for potential biodiesel production.

Edible Growth Medium: A New Window for Probiotic Research

Conventional growth media for microbes contains lots of non-edible components that are harmful to consume when the organism is ready to intake—like probiotics growing in chemical media (Lactobacillus grown in MRS media). The study was conducted to develop an edible and low-cost growth media that supports the growth of probiotics Lactic Acid bacteria for the enhancement of probiotic research. The 04 isolates of Lactobacillus (L. plantarum, L. rhamnosus, L. ferciminis and L. bifarmentans) and 02 Bifidobacterium (B. infantis and B. Bifidum) were used for the evaluation of medium efficacy. To formulate the edible culture media, 04 vegetables and 02 pulses were used. The media was formulated in different formulations. For Lactobacillus, maximum growth was observed at MM-2 media formulation that was about 15.62 log CFU/ml for L. plantarum and compared to MRS media that was 11.78 log CFU/ml. Bifidobaterium showed the highest viability at MW-1 edible media formulation which was about 12.72 log CFU/ml whereas in Bifidobacteria selective media the cell viability was 12.48 log CFU/ml. The edible media has no toxic or unhealthy effect on mice while trailing in an animal model and shows excellent results in encapsulation with alginate. In comparison with the performance of traditional chemical media, the formulated media were found to be cost-effective and safe for human consumption.

Augmentation of native microalgae based biofuel production through statistical optimization of campus sewage wastewater as low-cost growth media

The dependence of fresh-water for biomass growth is a major drawback in third generation microalgae biofuels, which need to be replaced with alternate sources. Optimizing nutrient concentrations already present in wastewater and its utilization towards microalgae growth could be a sustainable approach. In the present study, native microalga Chlorella thermophila (MF179624) was isolated and identified as model strain to optimize low-nutrient content campus sewage wastewater (CSW) using central composite design (CCD) followed by steepest ascent method (SAM). In consideration to the statistical optimization, addition of 325 mg L−1 and 1.8 g L−1 of KH2PO4 and NaNO3 resulted in 60% enhancement of biomass yield (2.59 g L−1) with two fold lipid productivity (81.38 mg L−1 d−1). In addition, substantial nutrient removal of ammonia (98.48 ± 1.52%), nitrate (86.37 ± 3.73%), phosphate (73.83 ± 4.28%), along with COD (82.53 ± 4.37%) were achieved. Further, TGA, FTIR, and 1H-NMR based characterization of lipid revealed its potential as a biofuel feedstock. To confirm that, two-step acid-base catalytic transesterification reaction was performed, which resulted in 474.42 mg L−1 FAME yield containing 85.14% C16 and C18.

Significantly enhanced biomass production of a novel bio-therapeutic strain Lactobacillus plantarum (AS-14) by developing low cost media cultivation strategy

BackgroundProbiotic bacteria are becoming an important tool for improving human health, controlling diseases and enhancing immune responses. The availability of a cost effective cultivation conditions has profound effect on the efficiency and role of probiotic bacteria. Therefore the current study was conducted with an objective to develop a low cost growth medium for enhancing the biomass production of a bio-therapeutic bacterial strain Lactobacillus plantarum AS-14. In this work the isolation of Lactobacillus plantarum AS-14 bacterial strain was carried out from brinjal using cheese whey as a main carbon source. Moreover, the effect of four other nutritional factors besides cheese whey was investigated on the enhanced cell mass production by using response surface methodology (RSM).ResultsThe best culture medium contained 60 g/l cheese whey, 15 g/l glucose and 15 g/l corn steep liquor in addition to other minor ingredients and it resulted in maximum dry cell mass (15.41 g/l). The second-order polynomial regression model determined that the maximum cell mass production (16.02 g/l) would be obtained at temperature 40°C and pH 6.2. Comparative studies showed that cultivation using cheese whey and corn steep liquor with other components of the selected medium generated higher biomass with lower cost than that of De Man, Rogosa and Sharpe (MRS) medium under similar cultivation conditions (pH 6.2 and temperature 40°C).ConclusionIt is evident that the cell biomass of L. Plantarum AS-14 was enhanced by low cost cultivation conditions. Moreover, corn steep liquor and ammonium bisulphate were perceived as low-cost nitrogen sources in combination with other components to substitute yeast extract. Of all these factors, cheese whey, corn steep liquor, yeast extract and two operating conditions (temperature and pH) were found to be the most significant parameters. Thus the cost effective medium developed in this research might be used for large-scale commercial application where economics is quite likely important.

PAH removal by immobilized bacterial cells-support systems using low-cost culture media for biomass production

The use of immobilized biomass for polycyclic aromatic hydrocarbon (PAH) removal from a liquid phase is a very promising technology. For this technology to be economically viable, the biomass production and immobilization should be as cost-effective as possible. The aim of this work was to produce a low-cost PAH removal system consisting of an immobilized biomass on different supports. A co-culture formed by two PAH-degrading bacteria (Pseudomonas monteilii P26 and Gordonia sp. H19, autochthonous Patagonian strains) was used. Industrial by-products such as sugar cane molasses, corn steep liquor, whey permeate and crude glycerol were used in combination to formulate different low-cost growth media. Naphthalene, phenanthrene and pyrene removal was evaluated using immobilized bacteria in polyurethane foam cubes, in sand and in calcium alginate beads. The growth of P. monteilii P26 and Gordonia sp. H19 was satisfactory in the different media assayed. The culture medium containing 1% corn steep liquor-2% molasses was selected for biomass production for subsequent immobilization. The removal of PAHs in different immobilization systems could be attributed to both the supports and the bacteria (up to 88.9% pyrene removal in 12 days); thus, immobilized cell systems for removing PAHs from an aqueous phase are proposed.

Biotransformation of major ginsenoside Rb1 to pharmacologically active ginsenoside Rg3 through fermentation by Weissella hellenica DC06 in newly developed medium

The study was conducted to develop an edible and low cost growth medium for cultivation of Weissella hellenica DC06, a lactic acid bacteria (LAB) and to study whether, the medium is suitable for bioconversion of major ginsenoside Rb1 into ginsenoside Rg3 through fermentation by W. hellenica DC06. Fourteen different media compositions were investigated to cultivate W. hellenica DC06. Among these, W. hellenica DC06 exhibited the highest growth in media containing 20 g/l radish, 20 g/l glucose, and 10 g/l yeast extract (Medium 3). The optical density of W. hellenica DC06 cultivated in medium 3 reached 1.8 (1.066 x 1010 CFU/ml) after 24 h of incubation. Importantly, the optimized medium was approximately four times cheaper compared to MRS medium. In addition to being economical, the new medium was also edible. Also W. hellenica DC06 showed strong fermentation ability in newly developed medium regarding on major ginsenoside Rb1 biotransformation. Ginsenoside Rb1 was converted into pharmacologically active ginsenoside Rg3 in new medium. In contrast,W. hellenica DC06 showed weak fermentation ability in MRS medium where ginsenoside Rb1 was converted intoginsenoside Rd. The transformation products were analyzed by TLC, and HPLC. Within seven days of fermentation, almost all ginsenoside Rb1 was decomposed and converted into Rg3 in optimized medium. W. hellenica DC06 hydrolyzed two glucose moieties attached to the C-20 position of the ginsenoside Rb1aglyconeand synthesized Rg3 in newly developed medium.Bangladesh J. Sci. Ind. Res. 51(4), 271-278, 2016

Evaluation of an Inexpensive Growth Medium for Direct Detection of Escherichia coli in Temperate and Sub-Tropical Waters.

The cost and complexity of traditional methods for the detection of faecal indicator bacteria, including E. coli, hinder widespread monitoring of drinking water quality, especially in low-income countries and outside controlled laboratory settings. In these settings the problem is exacerbated by the lack of inexpensive media for the detection of E. coli in drinking water. We developed a new low-cost growth medium, aquatest (AT), and validated its use for the direct detection of E. coli in temperate and sub-tropical drinking waters using IDEXX Quanti-Tray®. AT was compared with IDEXX Colilert-18® and either EC-MUG or MLSB for detecting low levels of E. coli from water samples from temperate (n = 140; Bristol, UK) and subtropical regions (n = 50, Pretoria/Tshwane, South Africa). Confirmatory testing (n = 418 and 588, respectively) and the comparison of quantitative results were used to assess performance. Sensitivity of AT was higher than Colilert-18® for water samples in the UK [98.0% vs. 86.9%; p<0.0001] and South Africa [99.5% vs. 93.2%; p = 0.0030]. There was no significant difference in specificity, which was high for both media (>95% in both settings). Quantitative results were comparable and within expected limits. AT is reliable and accurate for the detection of E. coli in temperate and subtropical drinking water. The composition of the new medium is reported herein and can be used freely.

Violet pigment production from liquid pineapple waste by Chromobacterium violaceum UTM5 and evaluation of its bioactivity

Liquid pineapple waste, a novel nutritious low cost growth medium. Crude violet pigment shows bioactivity. This is the first report on the production of violet pigment using liquid pineapple waste medium.

Low-Cost Biodegradation and Detoxification of Textile Azo Dye C.I. Reactive Blue 172 byProvidencia rettgeriStrain HSL1

Present study focuses on exploitation of agricultural waste wheat bran (WB) as growth medium for degradation of textile azo dye C.I. Reactive Blue 172 (RB 172) using a single bacteriumP. rettgeristrain HSL1 (GenBank accession numberJX853768.1). The bacterium was found to completely decolorize 50 mg L−1of dye RB 172 within 20 h at 30 ± 0.2°C under microaerophilic incubation conditions. Additionally, significant reduction in COD (85%) and TOC (52%) contents of dye decolorized medium was observed which suggested its mineralization. Induction in the activities of azoreductase (159%) and NADH-DCIP reductase (88%) provided an evidence for reductive cleavage of dye RB 172. The HPLC, FTIR, and GC-MS analysis of decolorized products confirmed the degradation of dye into various metabolites. The proposed metabolic pathway for biodegradation of RB 172 has been elucidated which showed the formation of 2 intermediate metabolites, namely, 4-(ethenylsulfonyl) aniline and 1-amino-1-(4-aminophenyl) propan-2-one. The acute and phytotoxicity evaluation of degraded metabolites suggests that bacterial strain favors the detoxification of dye RB 172. Thus, WB could be utilized as a low-cost growth medium for the enrichment of bacteria and their further use for biodegradation of azo dyes and its derivatives containing wastes into nontoxic form.

Ammonium removal from anaerobically treated effluent by Chlamydomonas acidophila

Several batch culture studies were carried out to evaluate an anaerobically treated effluent as a low-cost growth medium for the microalga Chlamydomonas acidophila and to study the effectiveness of the microalga in removing NH4-N from the effluent. An initial decrease in the effluent pH to 3 was required for adequate growth of C. acidophila and removal of NH4-N. Growth of the microalgae was inhibited at high light intensity (224μmolphotonsm(-2)s(-1) at the surface of the vessels). However, the growth was not greatly affected by the high solid content and turbidity of the effluent. The microalga was able to grow in media containing NH4-N at concentrations of up to 1000mgL(-1) (50% of effluent) and to remove 88mg of NH4-NL(-1) in 10days. C. acidophila therefore appears a promising agent for the removal of NH4-N from anaerobically treated effluents.

In vitro Detection and Optimization of Streptokinase Production by Two Streptococcal Strains in a Relatively Low Cost Growth Medium

This study sought to demonstrate the optimization of Streptokinase Production. Enzyme production was monitored during the growth of both Streptococcus pyogenes and Streptococcus equisimilis in different media. Adjustment of the pH for culture media of S. pyogenes and S. equisimilis, every 12 hours during incubation, significantly increased the enzyme production levels, when both microbes were grown on Strep-base medium. The best carbon source for streptokinase production was glucose of both S. pyogenes and S. equisimilis, while mannitol and sorbitol were found to be improper carbon sources. Yeast extract, and casein could be used as the primary source of organic nitrogen for streptokinase production, when the microbes were allowed to grow on Strep-base medium. The highest levels of the enzyme production were obtained with 1.5 % (w/v) tryptone and 1.5 % (w/v) casein for S. equisimilis and S. pyogenes, respectively. Detection of streptokinase produced was by the common casein digestion method and by the more sensitive chromozym substrate digestion method. Moreover, the enzyme was assayed electrochemically using the protamine-sensitive electrode to compare different methods of detection. Results obtained from electrochemical method were very close to that obtained with other methods. These results offer alternative and reliable method for streptokinase detection during microbial growth. It provides a faster and less expensive technique for streptokinase determination especially when there is a need to detect the enzyme in turbid media.

Utilization of tofu whey pre-treated by electromembrane process as a growth medium for Lactobacillus plantarum LB17

Lactobacillus plantarum is a probiotic microorganism which can use oligosaccharides like stachyose and raffinose during fermentations. Tofu whey (TW), a by-product of tofu production, is a good source of carbohydrates, mainly sucrose, raffinose and stachyose, as well as protein and magnesium (from the coagulant agent). In this context, the objectives of this study were to study the efficiency of electromembrane processes on salt (conventional electrodialysis) and protein (bipolar membrane electroacidification) recovery from the TW and to evaluate the potential of a partially demineralized pre-treated TW as a growth medium for L. plantarum. It appeared that skimming and demineralization of the TW allowed the recovery of almost 45% and 54% of the initial proteins and minerals contents respectively. However, the electroacidification process was inefficient for the precipitation of residual proteins in the TW. The demineralization level of the TW did not have a significant effect on the viable counts obtained for L. plantarum in demineralized skimmed tofu whey (DSTW)-based media. During fermentations, more than 60% of the initial contents of stachyose, raffinose and sucrose in TW were metabolized by the bacteria. These results suggest that the DSTW could be used as a potential low cost growth medium for lactobacilli and that the coagulant agent and protein recovered could be reused in tofu process to increase yield.

Nisin production utilizing skimmed milk aiming to reduce process cost

Nisin is a natural additive for conservation of food, pharmaceutical, and dental products and can be used as a therapeutic agent. Nisin inhibits the outgrowth of spores, the growth of a variety of gram-positive and gram-negative bacteria. This study was performed to optimize large-scale nisin production in skimmed milk and subproducts aiming at low-costs process and stimulating its utilization. Lactococcus lactis American Type Culture Collection (ATCC) 11454 was developed in a rotary shaker (30 degrees C/36 h/100 rpm) in diluted skimmed milk and nisin activity, growth parameters, and media components were also studied. Nisin activity in growth media was expressed in arbitrary units (AU/mL) and converted to standard nisin concentration (Nisaplin, 25 mg of pure nisin is 1.0x10(6) AU/mL). Nisin activity in skimmed milk 2.27 g(total solids) was up to threefold higher than transfers in skimmed milk 4.54 g(total solids) and was up to 85-fold higher than transfers in skimmed milk 1.14 g(total solids). L. lactis was assayed in a New Brunswick fermentor with 1.5 L of diluted skimmed milk (2.27 g(total solids)) and airflow of 1.5 mL/min (30 degrees C/36/200 rpm), without pH control. In this condition nisin activity was observed after 4 h (45.07 AU/mL) and in the end of 36 h process (3312.07 AU/mL). This work shows the utilization of a low-cost growth medium (diluted skimmed milk) to nisin production with wide applications. Furthermore, milk subproducts (milk whey) can be exploited in nisin production, because in Brazil 50% of milk whey is disposed with no treatment in rivers and because of high organic matter concentrations it is considered an important pollutant. In this particular case an optimized production of an antimicrobial would be lined up with industrial disposal recycling.